Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026850 (muscular dystrophy)
 5,870 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

beta-Sarcoglycan, one of the subunits of the sarcoglycan complex, is a transmembranous glycoprotein which associates with dystrophin and is the molecule responsible for beta-sarcoglycanopathy, a Duchenne-like autosomal recessive muscular dystrophy. To develop an animal model of beta-sarcoglycanopathy and to clarify the role of beta-sarcoglycan in the pathogenesis of the muscle degeneration in vivo, we developed beta-sarcoglycan-deficient mice using a gene targeting technique. beta-Sarcoglycan-deficient mice (BSG(-)(/-)mice) exhibited progressive muscular dystrophy with extensive degeneration and regeneration. The BSG(-)(/-)mice also exhibited muscular hypertrophy characteristic of beta-sarcoglycanopathy. Immunohistochemical and immunoblot analyses of BSG(-)(/-)mice demonstrated that deficiency of beta-sarcoglycan also caused loss of all of the other sarcoglycans as well as of sarcospan in the sarcolemma. On the other hand, laminin-alpha2, alpha- and beta-dystroglycan and dystrophin were still present in the sarcolemma. However, the dystrophin-dystroglycan complex in BSG(-)(/-)mice was unstable compared with that in the wild-type mice. Our data suggest that loss of the sarcoglycan complex and sarcospan alone is sufficient to cause muscular dystrophy, that beta-sarcoglycan is an important protein for formation of the sarcoglycan complex associated with sarcospan and that the role of the sarcoglycan complex and sarcospan may be to strengthen the dystrophin axis connecting the basement membrane with the cytoskeleton.
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PMID:Loss of the sarcoglycan complex and sarcospan leads to muscular dystrophy in beta-sarcoglycan-deficient mice. 1044 21

In the field of muscular dystrophy, advances in understanding the molecular basis of the various disorders in this group have been rapidly translated into readily applicable diagnostic tests, allowing the provision of more accurate prognostic and genetic counselling. The limb-girdle muscular dystrophies (LGMD) have recently undergone a major reclassification according to their genetic basis. Currently 13 different types can be recognized. Amongst this group, increasing diversity of the mechanisms involved in producing a muscular dystrophy phenotype is emerging. Recent insights into the involvement of the dystrophin glycoprotein complex in muscular dystrophy suggests that its members may play distinct or even multiple roles in the maintenance of muscle fibre integrity. In other forms of LGMD, proteins have been implicated which may be important in intracellular signalling, vesicle trafficking or the control of transcription. As these various mechanisms are more fully elucidated, further insights will be gained into the pathophysiology of muscular dystrophy. At a practical level, despite the marked heterogeneity of this group real progress can at last be made in determining a precise diagnosis.
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PMID:The limb-girdle muscular dystrophies-multiple genes, multiple mechanisms. 1046 40

To investigate mechanisms in the pathogenesis of cardiomyopathy associated with mutations of the dystrophin-glycoprotein complex, we analyzed genetically engineered mice deficient for either alpha-sarcoglycan (Sgca) or delta-sarcoglycan (Sgcd). We found that only Sgcd null mice developed cardiomyopathy with focal areas of necrosis as the histological hallmark in cardiac and skeletal muscle. Absence of the sarcoglycan-sarcospan (SG-SSPN) complex in skeletal and cardiac membranes was observed in both animal models. Loss of vascular smooth muscle SG-SSPN complex was only detected in Sgcd null mice and associated with irregularities of the coronary vasculature. Administration of a vascular smooth muscle relaxant prevented onset of myocardial necrosis. Our data indicate that disruption of the SG-SSPN complex in vascular smooth muscle perturbs vascular function, which initiates cardiomyopathy and exacerbates muscular dystrophy.
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PMID:Disruption of the sarcoglycan-sarcospan complex in vascular smooth muscle: a novel mechanism for cardiomyopathy and muscular dystrophy. 1048 11

In humans, mutations in the genes encoding components of the dystrophin-glycoprotein complex cause muscular dystrophy. Specifically, primary mutations in the genes encoding alpha-, beta-, gamma-, and delta-sarcoglycan have been identified in humans with limb-girdle muscular dystrophy. Mice lacking gamma-sarcoglycan develop progressive muscular dystrophy similar to human muscular dystrophy. Without gamma-sarcoglycan, beta- and delta-sarcoglycan are unstable at the muscle membrane and alpha-sarcoglycan is severely reduced. The expression and localization of dystrophin, dystroglycan, and laminin-alpha2, a mechanical link between the actin cytoskeleton and the extracellular matrix, appears unaffected by the loss of sarcoglycan. We assessed the functional integrity of this mechanical link and found that isolated muscles lacking gamma-sarcoglycan showed normal resistance to mechanical strain induced by eccentric muscle contraction. Sarcoglycan-deficient muscles also showed normal peak isometric and tetanic force generation. Furthermore, there was no evidence for contraction-induced injury in mice lacking gamma-sarcoglycan that were subjected to an extended, rigorous exercise regimen. These data demonstrate that mechanical weakness and contraction-induced muscle injury are not required for muscle degeneration and the dystrophic process. Thus, a nonmechanical mechanism, perhaps involving some unknown signaling function, likely is responsible for muscular dystrophy where sarcoglycan is deficient.
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PMID:Muscle degeneration without mechanical injury in sarcoglycan deficiency. 1048 93

The sarcoglycan complex has been well characterized in striated muscle, and defects in its components are associated with muscular dystrophy and cardiomyopathy. Here, we have characterized the smooth muscle sarcoglycan complex. By examination of embryonic muscle lineages and biochemical fractionation studies, we demonstrated that epsilon-sarcoglycan is an integral component of the smooth muscle sarcoglycan complex along with beta- and delta-sarcoglycan. Analysis of genetically defined animal models for muscular dystrophy supported this conclusion. The delta-sarcoglycan-deficient cardiomyopathic hamster and mice deficient in both dystrophin and utrophin showed loss of the smooth muscle sarcoglycan complex, whereas the complex was unaffected in alpha-sarcoglycan null mice in agreement with the finding that alpha-sarcoglycan is not expressed in smooth muscle cells. In the cardiomyopathic hamster, the smooth muscle sarcoglycan complex, containing epsilon-sarcoglycan, was fully restored following intramuscular injection of recombinant delta-sarcoglycan adenovirus. Together, these results demonstrate a tissue-dependent variation in the sarcoglycan complex and show that epsilon-sarcoglycan replaces alpha-sarcoglycan as an integral component of the smooth muscle dystrophin-glycoprotein complex. Our results also suggest a molecular basis for possible differential smooth muscle dysfunction in sarcoglycan-deficient patients.
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PMID:epsilon-sarcoglycan replaces alpha-sarcoglycan in smooth muscle to form a unique dystrophin-glycoprotein complex. 1048 49

A dystrophin-containing glycoprotein complex (DGC) links the basal lamina surrounding each muscle fibre to the fibre's cytoskeleton, providing both structural support and a scaffold for signalling molecules. Mutations in genes encoding several DGC components disrupt the complex and lead to muscular dystrophy. Here we show that mice deficient in alpha-dystrobrevin, a cytoplasmic protein of the DGC, exhibit skeletal and cardiac myopathies. Analysis of double and triple mutants indicates that alpha-dystrobrevin acts largely through the DGC. Structural components of the DGC are retained in the absence of alpha-dystrobrevin, but a DGC-associated signalling protein, nitric oxide synthase, is displaced from the membrane and nitric-oxide-mediated signalling is impaired. These results indicate that both signalling and structural functions of the DGC are required for muscle stability, and implicate alpha-dystrobrevin in the former.
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PMID:Role for alpha-dystrobrevin in the pathogenesis of dystrophin-dependent muscular dystrophies. 1055 19

The laminin receptor alpha7beta1 is enriched at the myotendinous junctions, and mice with a targeted inactivation of the alpha7 gene develop a form of muscular dystrophy that primarily affects this structure. By ultrastructural analysis of alpha7-deficient mice, in comparison with wild-type and mdx mice, we attempted to elucidate the role of alpha7 integrin for the integrity and function of the myotendinous junctions. Ultrastructurally, myotendinous junctions of alpha7-deficient myofibers lose their interdigitations and the myofilaments retract from the sarcolemmal membrane, whereas the lateral side of the myofibers remains morphologically normal. The basement membrane at the myotendinous junctions in alpha7 -/- mice is significantly broadened, and immunogold-histochemistry has demonstrated that the laminin alpha2 chain is not localized here but, instead, in the matrix of the neighboring tendon. In contrast, mdx mice have normal myotendinous junctions, with a matrix protein pattern also found in wild-type mice, however the lateral sides of the myofibers are severely damaged. These results suggest that the alpha7beta1 integrin is a major receptor connecting the muscle cell to the tendon and helps to organize the myotendinous junction, whereas the dystrophin-glycoprotein complex is necessary for the lateral integrity of the muscle cell.
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PMID:Organization of the myotendinous junction is dependent on the presence of alpha7beta1 integrin. 1061 9

Mutations in genes encoding for the sarcoglycans, a subset of proteins within the dystrophin-glycoprotein complex, produce a limb-girdle muscular dystrophy phenotype; however, the precise role of this group of proteins in the skeletal muscle is not known. To understand the role of the sarcoglycan complex, we looked for sarcoglycan interacting proteins with the hope of finding novel members of the dystrophin-glycoprotein complex. Using the yeast two-hybrid method, we have identified a skeletal muscle-specific form of filamin, which we term filamin 2 (FLN2), as a gamma- and delta-sarcoglycan interacting protein. In addition, we demonstrate that FLN2 protein localization in limb-girdle muscular dystrophy and Duchenne muscular dystrophy patients and mice is altered when compared with unaffected individuals. Previous studies of filamin family members have determined that these proteins are involved in actin reorganization and signal transduction cascades associated with cell migration, adhesion, differentiation, force transduction, and survival. Specifically, filamin proteins have been found essential in maintaining membrane integrity during force application. The finding that FLN2 interacts with the sarcoglycans introduces new implications for the pathogenesis of muscular dystrophy.
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PMID:Filamin 2 (FLN2): A muscle-specific sarcoglycan interacting protein. 1062 22

The membrane-spanning dystrophin glycoprotein complex mediates an indirect linkage between the actin-based cytoskeleton and the extracellular matrix. Although expressed by diverse cell types, genetic lesions of members of this complex result in muscular dystrophy phenotypes emphasizing the importance of these interactions in muscle cells. We have characterized interactions between dystrophin family members and dystroglycan: cytoskeletal and transmembrane components of the complex, respectively. Our results demonstrate that both the WW and EF hand domains of dystrophin and utrophin, an autosomal homologue of dystrophin, directly bind the cytoplasmic domain of dystroglycan. Furthermore, alpha-dystrobrevin, a more distantly related dystrophin family member which lacks a WW domain but contains the EF hand domain, binds dystroglycan. This is the first demonstration of a direct interaction between a dystrobrevin or utrophin and dystroglycan, and has implications for the organization of the dystrophin glycoprotein complex and the use of dystrophin homologues in muscular dystrophy therapy.
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PMID:WW and EF hand domains of dystrophin-family proteins mediate dystroglycan binding. 1066 92

Rigid spine syndrome is a term first proposed by Dubowitz to describe a subset of patients affected by myopathy with early spinal contractures as a prominent feature. While spinal rigidity is a nonspecific feature, found in Emery-Dreifuss muscular dystrophy and in some congenital myopathies, it is also a prominent feature in a group of patients with merosin-positive congenital muscular dystrophy, where it is generally associated with stable or only slowly progressive weakness and early respiratory insufficiency. Recently, the first locus for congenital muscular dystrophy in association with rigid spine syndrome was mapped to chromosome 1p35-p36 in consanguineous Moroccan, Turkish, and Iranian families. We present here a detailed phenotypic description of the familial syndrome linked to this locus, describing 4 siblings (3 boys and 1 girl) of Northern European-American heritage who are the offspring of a nonconsanguineous marriage. All 4 siblings were affected by hypotonia and prominent neck weakness in infancy, early spinal rigidity, and early scoliosis. After initial improvement, muscle strength stabilizes or slowly declines, and skeletal deformities and respiratory insufficiency supervene. Muscle biopsy in an affected child at age 9 months revealed minimal, nonspecific myopathic changes, leading to a diagnosis of "minimal change myopathy." Muscle biopsy in his sibling, at the age of 14 years, revealed chronic and severe myopathic (dystrophic) changes, with normal staining for laminin-2 and for proteins of the dystrophin-glycoprotein complex. A possible explanation for these biopsy findings is that magnetic resonance imaging of the thighs reveals stereotyped selective muscle involvement, with the selectivity more pronounced early in the disease course followed by widespread muscular signal abnormalities in the late stages of the disease. In this family, linkage to the chromosome 1p rigid spine syndrome locus (RSMD1) is supported by maximum LOD scores for several markers of 1.81 at theta = 0, representing the maximum statistical power possible for this family. In combination with the previous report, this syndrome is linked to the RSMD1 locus with a summated maximum LOD score of 6.29, and analysis of recombination events in our family narrows the previously reported RSMD1 locus to 3 centiMorgans.
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PMID:Congenital muscular dystrophy with rigid spine syndrome: a clinical, pathological, radiological, and genetic study. 1066 83


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